PROJECT SUMMARY Perinatal hypoxic-ischemia (HI) is a critical perinatal event that is characterized by exposure to low oxygen and decreased blood flow during the perinatal period, ultimately leading to hypoxic-ischemic encephalopathy (HIE) in newborn. Perinatal HIE happens with an incidence of 1-8 cases per 1000 newborns, and is associated with the short-term medical complications and the long-term neurological disorders. The treatment of infants with HIE remains a difficult task for neonatologists in neonatal management, albeit hypothermia, which is the standard of clinical care for newborns with HIE, has been proven to provide some degree of success in neonatal care. Thus, there is an urgent need to uncover new insights into the cellular and molecular mechanisms underlying the pathophysiology of perinatal HIE, and to develop new effective interventions. We demonstrated that the c-type natriuretic peptide (CNP) deficiency increased the vulnerability of the neonatal brains to HIE in mouse pups, and our preliminary data showed that HI insult downregulated brain CNP levels in mouse pups. These findings revealed a novel innate neuroprotectant role of CNP in the setting of neonatal HIE mouse model. However, the mechanisms underlying the innate neuroprotectant role of CNP in the neonatal brain remain unknown. The action of CNP is mediated by CNP cognate receptors NPR2 and NPR3, which exhibit cell-specific expression in neurons and cerebrovascular endothelial cells, respectively. Based these findings, we propose the following studies to investigate the molecular mechanisms of CNP-mediated protective effects through NPR2- and/or NPR3-dependent pathways using in vitro and in vivo models. Furthermore, we test the hypothesis that intranasal administration of CNP provides protective effects and synergizes the effects of hypothermia treatment on perinatal HIE in mouse pups. The proposed study is built upon strong scientific premise, and will explore a novel concept with an innovative and mechanistic approach. The goal of this application is to determine the impact and underlying mechanisms of CNP-mediated protective effects in the setting of perinatal HIE in mouse pups, and of critical importance, to explore the therapeutic potential of CNP treatment for perinatal HIE. The outcome of the proposed study will not only advance our understanding of the pathophysiology of neonatal HIE, but promote the development of new CNP-based therapeutic strategies for perinatal HIE treatment in newborn.